When Nvidia went from 600 tp 700 to 900 series, it's new architecture, fermi, kepler, maxwell, etc. Each new step brings new things. 780 to 780ti, TI has may more cuda cores enabled. These things are different.
300 series AMD cards are the same chips, same number of cores, etc as the 200 series. This isn't a new chip. Same chip, new name. Different than what Nvidia has done.